Compensation payments to victims of the Rana Plaza factory collapse are due to start next month - but campaigners admit funds still fall far short of the $40m needed to make payments to all workers.

Unions and labour activists are now stepping up calls for brands to pay into the Rana Plaza Donors Trust Fund ahead of the 24 March launch date for the claims process to begin.

Claims processing will be carried out from an office based in Savar, the town near Dhaka where the Rana Plaza building was located. Potential beneficiaries will be invited to the office to make their claim.

A pre-claim legal team will work with each claimant to ensure they fully understand what claims can be made for and how they will be decided. A hotline in Savar will be launched at the same time to respond to any questions or enquiries about the claims process.

It is expected that first payments under the Rana Plaza Arrangement will be provided by the first anniversary of the disaster on 24 April.

The Fund was opened at the beginning of February, with an initial target of $10m, calculated to be the amount needed to pay first installments to all the potential claimants.

A total of $40 m is needed in total to cover full payments to over 3000 workers and families of those killed - but campaigners say "there is a long way to go" before the $40m is found.  

So far, seven brands have all publicly pledged initial donations, including Bon Marche, El Corte Ingles and Loblaw, Inditex, Mango, Mascot, Loblaw and Premier Clothing.

But Primark is singled out as the only signatory company of the Arrangement yet to make a contribution.

"We are now calling on Primark and all the other brands linked to Rana Plaza to stop delaying and pay up," says Labour Behind the Label's Sam Maher.

Other companies claimed to have links to Rana Plaza are said to include Adler, Auchan, Benetton, Camaieu, Carrefour, Carrona, Cato Fashions, Children's Place, JC Penney, Kids for Fashion, Lee Cooper, Manifattura Corona, Mango, Matalan, NKD, Premier Clothing, Primark, PVT (Texman), Store 21, Yes Zee, and Walmart.